CN105049040B - A kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS - Google Patents

A kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS Download PDF

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CN105049040B
CN105049040B CN201510354798.4A CN201510354798A CN105049040B CN 105049040 B CN105049040 B CN 105049040B CN 201510354798 A CN201510354798 A CN 201510354798A CN 105049040 B CN105049040 B CN 105049040B
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李铎
吴红卫
田原
陈杰华
顾思洪
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Wuhan Institute of Physics and Mathematics of CAS
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Abstract

The invention discloses a kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS, including：1PPS signals according to GNSS inputs generate n time interval signal in a cycle T；Utilize the frequency of time interval signal measurement CPT atomic clock output signals, time interval signal measurement one CPT atomic clock output signal of record；Multiple measured values are obtained in a cycle T, the actual output frequency after the average value of multiple measured values is carried out into Kalman filtering processing as CPT atomic clocks within the cycle；And the frequency departure using actual output frequency and the difference of predeterminated frequency as CPT atomic clocks；According to frequency departure by the frequency correction of CPT atomic clock output signals to predeterminated frequency.The present invention can suppress the frequency drift of CPT atomic clocks, improve the degree of accuracy of CPT atomic clocks and long-term stability；The frequency measuring method of offer increases substantially frequency-measurement accuracy on the premise of correction time interval is slightly increased.

Description

A kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS
Technical field
The invention belongs to atomic clock field, and in particular to one kind utilizes GPS (GNSS, Global Navigation Satellite System) receiver output pulse per second (PPS) (1PPS, 1pulse per second) correction quilt The method that ejector half Coherent Population Trapping imprisons (CPT, Coherent Population Trapping) atomic clock output frequency, by this The CPT atomic clocks that method is realized can obtain higher frequency stability and the degree of accuracy, can suppress frequency drift.
Background technology
CPT atomic clocks are a kind of New type atom clocks, and it has the characteristics that small volume, low in energy consumption, toggle speed is fast, can be extensive Applied to fields such as positioning, navigation, communication base station and fine timings.
CPT atomic clocks are using microwave to Vcsel (VCSEL, Vertical Cavity Surface Emitting Laser) it is modulated, frequency modulation polychromatic light is produced, the bi-coloured light being made up of the heterogeneous light positive and negative first order side band that is concerned with With atomic interaction, CPT state atoms can be prepared when microwave frequency is suitable, it is possible thereby to observe CPT phenomenons.Scan coupling The microwave frequency on laser is closed, the CPT signals in lorentzian curve are obtained, by microwave frequency corresponding to CPT signal peaks The referred to as centre frequency of CPT signals.The frequency frequency multiplication that the microwave frequency of CPT atomic clocks is exported by VCXO obtains, by microwave Frequency Locking obtains the atomic clock of high stability output frequency in the centre frequency of CPT signals.The centre frequency meeting of CPT signals Changed because of influences of factor such as variation of ambient temperature, laser intensity changes, cause the output frequency of atomic clock to deviate Standard output frequency.If it is known that the size of the frequency departure standard output frequency of CPT atomic clock output signals, it is possible to pass through Some means, such as the Clock Multiplier Factor of the microwave multiple-frequency chain by adjusting atomic clock circuit control system, the magnetic field of physical system Intensity etc., output frequency can be corrected to preset standard output frequency, improve the precision of atomic clock output frequency.
Due to being mounted with upper frequency stability on GNSS (such as GPS, GALILEO, GLONASS and BDS) every satellite With the atomic clock of the degree of accuracy, usually rubidium clock, caesium clock and passive hydrogen clock, therefore when can provide high-precision in coverage Between.The 1PPS that the GNSS satellite obtained by GNSS receiver exports can be used as high-precision time source, utilize CPT atomic clocks The time interval that output signal measurement obtains, using time interval as known quantity so as to instead release CPT atomic clock output signals Frequency.
Because signal from satellite transmission to receiver process and receiver introduces noise in itself so that connect by GNSS Shake, common receiver output be present relative to sequence corresponding to universal time in the 1PPS signal clocks sequence that receipts machine obtains 1PPS shake be up to 10-100ns, if being directly used as standard time source measurement CPT atomic clock output signals by the use of 1PPS Frequency can bring larger frequency measurement error.
The content of the invention
The defects of for prior art, the invention provides one kind to utilize GNSS correction Atomic Clocks Based on Coherent Population Trapping outputs The method of frequency, its object is to suppress the frequency drift of CPT atomic clocks, improve the precision of CPT atomic clock output signal frequencies.
It is including following the invention provides a kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS Step：
S1：Using the frequency of 1PPS signal measurement CPT atomic clocks, the difference of frequency measurement and predeterminated frequency is as frequency Deviation；
S2：According to the frequency departure by the frequency correction of CPT atomic clock output signals to predeterminated frequency.Wherein, this is pre- If frequency is given value, generally 10M.
Further, step S1 is specially：
S11：Generate the correcting controlling signal that the cycle is T；
S12：1PPS signals according to GNSS inputs generate n time interval signal in a cycle T；
S13：Utilize the frequency of time interval signal measurement CPT atomic clock output signals, a time interval signal measurement Record the frequency of a CPT atomic clock output signal；
S14：Multiple measured values are obtained in a cycle of the correcting controlling signal, by the average value of multiple measured values Actual output frequency after progress Kalman filtering processing as CPT atomic clocks within the cycle；And by the reality output frequently The frequency departure of rate and the difference of predeterminated frequency as CPT atomic clocks.
Further, step S11 is specially：
By carrying out cycle count to the frequency of CPT atomic clock output signals, periodic correcting controlling signal is obtained；Its In, a cycle is that T correcting controlling signal is made up of a high level and a low level, and the duration of high level is (T-t0), the low level duration is t0, t0Span be 1us-1ms.
Further, CPT atomic frequencies are obtained in the high level lasting time of the correcting controlling signal Deviation, according to frequency departure by the frequency correction of CPT atomic clock output signals to default frequency in the low duration Rate.
Further, step S12 is specially：
By carrying out cycle count to the frequency of CPT atomic clock output signals, periodic multiple-pulse signal strobe is obtained；
The pulse gate signal of H groups two is obtained according to the multiple-pulse signal strobe；
Each two pulse gates signal obtains a time interval signal by capturing 1PPS rising edge, is obtained n Time interval signal；Wherein H value is equal with n values.
Further, obtaining the pulse gate signal of H groups two is specially：
There is 2n pulse high level in a cycle T of the multiple-pulse signal strobe, each pulse high level continues Time is less than 2s more than 1s, and the spacing of preceding n rising edge of a pulse is ks, and the spacing of rear n rising edge of a pulse is also ks；1st Spacing between the rising edge of pulse high level and the rising edge of (n+1)th pulse high level is T ', the 1st pulse and (n+1)th Individual pulse is first group, and n-th of pulse that the 2nd pulse and the n-th+2 pulses are second group ... ... and the 2n pulse are H Group, the like obtain H group pulses, include high level and low level per group pulse, two pulse gates formed per group pulse Signal, the rising edge spacing of two pulses of two pulse gate signals is T ', obtains the pulse gate signal of H groups two altogether；Two pulses The cycle of signal strobe is T；Wherein, k is the integer more than 1.
Further, obtaining a time interval signal is specially：In a cycle T of correcting controlling signal, two arteries and veins Rushing signal strobe has two pulse high levels, first pulse high level duration detection 1PPS rising edge, when on 1PPS Rise along when arriving, time interval signal puts high level；In second pulse high level duration detection GPS 1PPS rising Edge, when GPS 1PPS rising edges arrive, time interval signal sets low level, so as to generate a time interval signal, time Blank signal provides time interval, for measuring CPT atomic clock output frequencies.
Further, in step s 13, the frequency of the CPT atomic clocks output signal isIts In, T '=NTc+τ1-τ2, Tc=1/fc, N is that the CPT atomic clocks measured in the high level lasting time of time interval signal are defeated Go out the number of signal rising edge；τ1、τ2The error brought for direct counting method, T' are high electricity in time interval signal a cycle Flat duration, TcFor the cycle of CPT atomic clock output signals.
Further, in step s 2, when the difference between the frequency of CPT atomic clock output signals and predeterminated frequency is big When the threshold value of setting, using coarse adjustment by the frequency correction of CPT atomic clock output signals to default frequency；
When the difference between the frequency and default frequency of CPT atomic clock output signals is less than the threshold value of setting, use Fine tuning is by the frequency correction of CPT atomic clock output signals to predeterminated frequency.
Wherein, coarse adjustment realizes that fine tuning passes through change by changing the Clock Multiplier Factor of the microwave multiple-frequency chain of circuit control system The electric current of field coil is realized in CPT atomic clock physical systems.
The present invention has advantages below compared with prior art：
(1) present invention proposes a kind of frequency measuring method, and this method is suppressed by average filter and Kalman filter 1PPS white noise, improves frequency-measurement accuracy.
(2) in a calibration cycle, n time interval signal, n time interval signal are obtained using GNSS 1PPS High level lasting time be in normal distribution, be used as reference measurement CPT atomic clock output signals by the use of the time in normal distribution Frequency obtain n measured value, these measurement errors equally meet normal distribution, using these measured values it is average after as one The actual output frequency of CPT atomic clocks, adds frequency-measurement accuracy in calibration cycle.Correction can be slightly increased using this method Frequency-measurement accuracy is increased substantially on the premise of time interval, further improves the precision of CPT atomic clock output signal frequencies.
(3) realize that the apparatus structure of the present invention is simple, signal transacting scheme can use digital methods to realize, relative to Traditional CPT atomic clocks only increase a time-to-digit converter (TDC, Time to Digital Convert).
Brief description of the drawings
Fig. 1 is H two pulse gate signal method schematic diagrames of generation in a cycle T of correcting controlling signal, passes through Fig. 1 Method H two pulse gate signals can be generated in a calibration cycle, each two pulse gates signal passes through capture 1PPS rising edge obtains a time interval signal, and H two pulse gate signals obtain n time interval signal, H and n's It is worth identical.
Fig. 2 is single frequency measurement method schematic diagram.When production method including time interval signal and utilization Between blank signal high level lasting time measurement CPT atomic clock output signal frequencies method.Wherein t1And t2For signal strobe High level lasting time, for capturing 1PPS rising edge.When T ' is that high level continues in time interval signal a cycle Between, TcFor the cycle of CPT atomic clock output signals, N is the rising of CPT atomic clock output signals in a high level lasting time Along number, τ1And τ2Value utilize TDC measurement.
Fig. 3 is the frequency measurement schematic diagram in a calibration cycle T.Wherein T is the cycle of correcting controlling signal, between correction Every identical with the value of calibration cycle, i.e., deviate preset standard output frequency according to the frequency values of CPT atomic clock output signals per T time The frequency of the size correction CPT atomic clock output signals of rate.N time interval signal is generated in a calibration cycle, it is each Individual time interval signal measurement one frequency measurement of record, is exported the average value of these values as CPT atomic clocks in T time The frequency values of signal.
Fig. 4 is a kind of schematic device that CPT atomic clocks are corrected using 1PPS.
Fig. 5 is relative to the newly-increased schematic device of traditional CPT atomic clocks present invention.
Fig. 6 is the CPT atomic clocks and the CPT atomic clock Allan variance comparison diagrams of not correction up that the present invention realizes.
The degree of accuracy for the CPT atomic clocks that Fig. 7 is realized using the present invention；The atomic clock degree of accuracy realized is entered in a short time Enter E-12 magnitudes.
Fig. 8 is Kalman filter flow chart.
Embodiment
In order to make the purpose , technical scheme and advantage of the present invention be clearer, it is right below in conjunction with drawings and Examples The present invention is further elaborated.It should be appreciated that the specific embodiments described herein are merely illustrative of the present invention, and It is not used in the restriction present invention.
The invention provides it is a kind of using GNSS receiver output 1PPS correct CPT atomic clock output frequencies method, GNSS is combined to the CPT atomic clocks with calibration function of realization with CPT atomic clocks can obtain degree of precision.This method The frequency of the 1PPS measurement CPT atomic clock output signals of GNSS receiver output can be utilized, is deviateed so as to obtain output frequency The size of preset standard output frequency, while the method combined using average filter and Kalman filter suppresses 1PPS shakes Caused frequency measurement error.Present invention also offers a kind of method of regulation CPT atomic clock output signal frequencies, by microwave multiple-frequency chain The regulation of Clock Multiplier Factor is as coarse adjustment, and the regulation of physical system field strength is as fine tuning.The method that coarse adjustment is combined with fine tuning It not only can accurately adjust the frequency of CPT atomic clock output signals while may insure that physical system field strength does not occur greatly Change so as to influenceing the stability of CPT atomic clocks.
The present invention increases atomic clock in existing CPT atomic clocks technical foundation and receives 1PPS semiotic functions.When each Between T, utilize the frequency of 1PPS signal measurement CPT atomic clock output signals, the measured value of frequency and preset standard output frequency Frequency departure of the difference as CPT atomic clocks, the microwave according to the frequency departure regulation CPT atomic clock circuit control systems obtained The Clock Multiplier Factor of frequency multiplier chain and the field strength of physical system, by the frequency correction of CPT atomic clock output signals to preset standard Frequency.Wherein the change of field strength can be realized by changing the electric current of field coil；
A kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS provided by the invention, it is specially：
A, using the frequency signal of local CPT atomic clocks output as elapsed time clock, by generating the cycle to clock count For T correcting controlling signal.As shown in figure 1, the correcting controlling signal of a cycle is by a high level and a low level group Into the duration of high level is (T-t0), the low level duration is t0, t0Span be 1us-1ms.Correcting The frequency of the high level lasting time measurement CPT atomic clock output signals of control signal, the measured value and preset standard of frequency are defeated Go out the difference of frequency as output frequency deviation, in low duration according to frequency departure correction CPT atomic clock output letters Number frequency.
B, H two pulse gate signals are generated.Specific method is：As shown in figure 1, by clock count, being controlled in correction Multiple pulse high levels are generated in the high level lasting time of signal processed, is low level outside pulse high level, thus obtains One multiple-pulse signal strobe, cycle are also T；There is 2n pulse high level in a cycle T of multiple-pulse signal strobe, and Each pulse high level duration is less than 2s more than 1s, in 2n pulse high level, arbitrary neighborhood in preceding n pulse high level (rising edge of i.e. the 1st pulse high level is upper with the 2nd pulse high level for ks for spacing between the rising edge of two pulses The spacing risen between is the k seconds, between the rising edge of the 2nd pulse high level and the rising edge of the 3rd pulse high level between It is k away from the spacing between the rising edge and the rising edge of n-th of pulse high level for (n-1)th pulse high level of k seconds ... ... Second)；The spacing in n pulse high level between the rising edge of two pulses of arbitrary neighborhood is also ks (i.e. (n+1)th pulse height afterwards Spacing between the rising edge of level and the rising edge of the n-th+2 pulse high levels is the k seconds, the n-th+2 pulse high levels it is upper Rise along the rising edge that the spacing between the rising edge of the n-th+3 pulse high levels is k the 2n-1 pulse high level of second ... ... Spacing between the rising edge of the 2n pulse high level is the k seconds), k is the integer more than 1.1st pulse high level Spacing between rising edge and the rising edge of (n+1)th pulse high level is T ' (rising edge of i.e. n-th pulse high level and the Spacing between the rising edge of n+1 pulse high level is T '-(n-1) k seconds).
It is first group to make the 1st pulse and (n+1)th pulse, and the 2nd pulse is second group with the n-th+2 pulses ... ... N-th of pulse and the 2n pulse be H groups, the like obtain H group pulses, per group pulse, one two pulse gate of composition are believed Number, two pulse gate signals are low level in addition to two pulses, the rising edge spacing of two pulses of two pulse gate signals For T ', the pulse gate signal of H groups two is obtained altogether；The cycle of two pulse gate signals is also T；Wherein H is two pulse gate signals Sum, its value is identical with n value.
C, triggers circuit is controlled to work by two pulse gate signals, the high level lasting time in two pulse gate signals Section triggers circuit work, when the rising edge of 1PPS signals arrives, the change occurs for the output of the triggers circuit, when 1PPS signals Rising edge when not arriving, the change does not occur for the output of the triggers circuit；Low level continues in two pulse gate signals Period triggers circuit does not work；
Each two pulse gates signal can obtain a time interval signal by capture time source 1PPS rising edge. As shown in Fig. 2 in a cycle T of two pulse gate signals, visited in first high level lasting time by triggers circuit 1PPS rising edge is surveyed, when 1PPS rising edges arrive, the time interval signal of triggers circuit output puts high level.Similarly Two high level lasting time detection 1PPS rising edge, when 1PPS rising edges arrive, time interval signal sets low level.This Sample just generates a cycle of time interval signal, and high level lasting time is T ' in a cycle T.T ' precision is by 1PPS Precision determine, utilize 1PPS provide the time measurement CPT atomic clock output signals with degree of precision frequency.
Specific measuring method as shown in Fig. 2 time interval signal high level lasting time, measure CPT atoms The number N of clock output signal rising edge.τ in Fig. 2 is measured by TDC1、τ2Value, can obtain：T'=NTc+τ1-τ2 (1)；Wherein TcFor the cycle of CPT atomic clock output signals.The frequency of CPT atomic clocks output signal is as available from the above equation：High level lasting time actually in time interval signal a cycle T is not T ', But error be present, this error be mainly derived from 1PPS shake caused by white noise, error is designated as Δ T.ThenThus the relative frequency measurement error brought is
D, in current GNSS receiver, the 1PPS clock sequences of GNSS receiver output are corresponding with universal time Sequence certain error ε be present.Usually, ε Normal Distributions ε~N (0, σ2)(5)；On the 1PPS of GNSS receiver output Rising along corresponding universal time to be designated as：ε0,1+ε1,2+ε2,3+ε3,...,x+εx,...(6)。
As shown in Fig. 2 there is a pulse high level in a cycle of time interval signal, if in pulse high level It is ε to rise along corresponding universal time0, then universal time corresponding to trailing edge is T '+εT', the high level of acquisition holds The continuous time is ε relative to the deviation delta T of standard timeT'-ε1, ε is the independent random stationary process of Normal Distribution.(εT',ε1 It is ε subset) 1PPS of common receiver output shake ε standard deviation sigma is 10-100ns, if directly using the side in C Method measures the frequency of CPT atomic clock output signals, and its frequency-measurement accuracy is not high.If we have found that εT′-ε1As variable ξx= εx+T′-εx(7)；Same Normal Distribution ξ~N (0,2 σ of ξ2)(8).Δ T and ξ is of equal value.
As shown in figure 3, the method in step C is used using the H generated in step B two pulse gate signals, N time interval signal can be obtained, and then the frequency of n CPT atomic clock output signal of record can be measured.By It is more stable in the frequency of CPT atomic clock output signals, the approximate clothes of n frequency measurement can be obtained according to formula (4) From normal distributionThe average value of the multiple measured values obtained in one calibration cycle T Compared to f0Error beWillAs CPT atoms in time T Clock actual output frequency, it is with respect to frequency-measurement accuracyIf only generate a time interval signal in identical time T to survey The frequency of CPT atomic clock output signals is measured, is with respect to frequency-measurement accuracyWherein T is slightly larger than T ', in identical correction time Under interval, frequency-measurement accuracy about improvesTimes.In the frequency side of the 1PPS correction CPT atomic clock output signals using GNSS In case, frequency-measurement accuracy is the higher the better.According to formula (4), frequency-measurement accuracy can be improved by reducing Δ T or increase T '.Δ T by GNSS system precision and receiver performance determine that T ' is manually set by us, but increasing T' means correction time interval It is elongated, when correction time, interval was long CPT atomic clocks will be caused to be corrected in time when there is deviation, and reduce CPT atomic clocks The precision of output signal.The present invention, can by obtaining multiple frequency measurements and then average method in a calibration cycle To obtain higher frequency-measurement accuracy in shorter correction interval, so as between correction is shortened on the premise of ensuring frequency-measurement accuracy Every improving the precision of CPT atomic clock output signal frequencies.The above method is referred to as average filter by us.
E, the rate-adaptive pacemaker value obtained in step C is handled by Kalman filtering, calculates filtering eligible result with presetting The difference of standard output frequency, the frequency of CPT atomic clock output signals is adjusted with obtained difference.CPT atoms are adjusted in the present invention The method of clock is divided into coarse adjustment and fine tuning.Coarse adjustment is by changing the frequency multiplication system of the microwave multiple-frequency chain of CPT atomic clock circuit control systems Number realizes that fine tuning is realized by changing the electric current of the field coil in CPT atomic clock physical systems.Believe when CPT atomic clocks export Number frequency departure preset standard frequency size be more than setting threshold value A when, using coarse adjustment；Believe when CPT atomic clocks export Number the size of frequency departure preset standard frequency when being less than threshold value A, using thin tuning.
The application utilizes the characteristics of 1PPS signals, it is proposed that a kind of measuring method of CPT atomic clocks output signal frequency, should Method can increase substantially measurement accuracy, shorten correction interval under conditions of frequency-measurement accuracy is met, it is former further to suppress CPT Secondary clock frequency drift, improve the degree of accuracy of CPT atomic clocks and stability.It also proposed a kind of CPT atomic clocks output frequency regulation side The combination of method, coarse adjustment and fine tuning can be not influence the stability of atomic clock while accurate adjustment CPT atomic frequencies.
Below in conjunction with the accompanying drawings, the present invention will be further described, and wherein CPT atomic clocks preset standard frequency is 10MHz, GNSS 1PPS comes from global positioning system (GPS, global position system).
A kind of method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS, it is comprised the concrete steps that：
Step 1：Start CPT atomic clocks.
Step 2：Using the frequency of CPT atomic clock output signals as elapsed time clock, as shown in figure 3, by CPT atomic clocks The rising edge of output signal, which counts, can obtain accurate correcting controlling signal, in a cycle T of correcting controlling signal N time interval signal is obtained, then the measurement record CPT on the basis of the high level lasting time of the time interval signal of acquisition The output valve of atomic clock, n time interval signal obtain n frequency measurement, as school after these frequency measurements are averaged The frequency of CPT atomic clock output signals in a cycle T of positive control signal.
The method of measurement CPT atomic clock output signal frequencies in a cycle T is specifically described below.By correcting controlling signal Cycle be set to 420s, n 10, t1And t2For 1.5s, k 2s, the high level lasting time in time interval signal a cycle T' is 400s, and time-to-digit converter uses TDC_GP21.First, it is by the 10MHz signal frequency splits that CPT atomic clocks export 1KHz.Then 0 is counted as to 1KHz signal-counts, first rising edge, when arriving 1KHz signals rising edge count value according to Secondary increase by 1.When count value is 420000, when next rising edge of 1KHz signals arrives, count value resets 0, by above-mentioned side Method loop cycle.As shown in figure 1, in count value 0-1499,2000-3499,4000-5499,6000-7499,8000-9499, 10000-11499,12000-13499,14000-15499,16000-17499,18000-19499,400000-401499, 402000-403499,404000-405499,406000-407499,408000-409499,410000-411499,412000- Multiple-pulse signal strobe is high level when 413499,414000-415499,416000-417499,418000-419499, is counted Be worth for other values when, multiple-pulse signal strobe is low level.By the above method one multiple-pulse signal strobe of generation, the cycle is 420s, there are 20 pulse high levels in a cycle.It is 1 group to make the 1st pulse and the 11st pulse, the 2nd pulse and the 12nd Individual pulse is one group, the like.10 group pulses have thus been obtained, a two pulse gate signals are formed per group pulse.Two The spacing of two rising edge of a pulses of pulse gate signal is 400s.One two pulse gate signal is by capturing 1PPS rising edges A time interval signal is obtained, using the method in Fig. 2, is visited in two pulse gate signals, first high level lasting time GPS 1PPS rising edge is surveyed, when GPS 1PPS rising edges arrive, time interval signal puts high level.Similarly at second Detection GPS 1PPS rising edge in high level lasting time, when GPS 1PPS rising edges arrive, time interval signal is put Low level.A time interval signal is thus generated, 10 signal strobes can generate 10 time interval signals.It is each The frequency of individual time interval signal measurement one CPT atomic clock output signal of record.Specific method is as follows：In time interval signal High level lasting time, the rising edges of CPT atomic clock output signals is counted, it is N that can obtain counting number, the τ in Fig. 21 And τ2Measured with time-to-digit converter TDC_GP21, following measured value T '=NT can be obtainedc+τ1-τ2(12)；TDC_GP21 Then there is τ by the use of CPT atomic clock output signals as clock source1-τ2=(d1-d2)×Tc(13)；Wherein d1And d2By TDC_GP21 Obtain, TcFor the cycle of CPT atomic clock output signals；Tc=1/fc(14) (13) (14) substitution (12) can be obtainedThe frequency of CPT atomic clock output signals has thus been measured using 1 time interval signal. 10 time interval signals can obtain 10 frequency measurements, as a calibration cycle after these frequency measurements are averaged Actual output frequency in 420s.
Step 3：The actual output frequency obtained in step 2 is further handled using Kalman filter, Kalman's filter Ripple device can filter out a part of white noise.As shown in figure 8, Kalman filter includes five fundamental equations, wherein representing noise The Q and R of parameter use assembly average, can measure in advance.The output of Kalman filter and preset standard output frequency Frequency departure of the 10MHz difference as CPT atomic clock output signals.
Step 4：Using the exemplary frequency deviation values of CPT atomic clock output signals as foundation, correction CPT atomic clock output signals Frequency.The regulative mode of the frequency of CPT atomic clock output signals has two kinds, respectively coarse adjustment and fine tuning：Coarse adjustment is micro- by adjusting The Clock Multiplier Factor of ripple frequency multiplier chain realizes that fine tuning is realized by adjusting the field coil electric current in physical system.When above-mentioned difference When absolute value is more than 2E-2Hz, the frequency coarse adjustment to CPT atomic clock output signals, output frequency is otherwise adjusted by fine tuning. The atomic clock performance realized by the above method is as shown in Figure 7.
Present invention also offers one kind to utilize GNSS correction coherent layout Trapping of Atoms clock output frequency systems, concrete structure As shown in figure 4, including circuit control system and physical system.Wherein circuit control system includes controller, digital analog converter, electricity Pressure/current converter circuit, bias device (Bias-Tee), VCXO, phaselocked loop, voltage controlled oscillator, current/voltage-converted electricity Road, analog-digital converter, time-to-digit converter and GNSS receiver, VCXO, phaselocked loop, voltage controlled oscillator form microwave times Frequency chain.Physical system includes laser generator, field coil, magnetic screen, atomic bubble and optical detection device.Current/voltage-converted The output end of the input connection optical detection device of circuit, the output end connection analog-digital converter of current/voltage converter circuit Input, the output end of analog-digital converter connect the input of analog-digital converter interface in controller, the first digital analog converter Input connection controller in the first digital analog converter interface output end, the first digital analog converter output end connection voltage/ Current converter circuit a input, voltage/current conversion circuit a output end connection Bias-Tee direct-flow input end, second The output end of second digital analog converter interface, the output of the second digital analog converter in the input connection controller of digital analog converter The voltage-controlled input of end connection VCXO, the output end of the reference signal input connection VCXO of phaselocked loop, phaselocked loop Configure the output end of phase-locked-loop configuration interface in interface input connection controller, the output end connection voltage controlled oscillator of phaselocked loop Input, the output end of voltage controlled oscillator is divided into two-way, connects Bias-Tee microwave input port, another way connection lock all the way Phase ring RF signal input end, Bias-Tee output end connect the input of laser generator in physical system, time figure The output end of time-to-digit converter interface, the output end of time-to-digit converter connect in the input connection controller of converter The input of time-to-digit converter interface in controller is connect, the output end of GNSS receiver connects 1PPS signals in controller Input, the input of the 3rd digital analog converter connect the output end of the 3rd digital analog converter interface in controller, the 3rd digital-to-analogue The output end connection voltage/current conversion circuit b of converter input, voltage/current conversion circuit b output end connection magnetic The input of field coil.
What's new module wherein in controller as shown in figure 5, including time interval signal generation module, frequency measurement module, Kalman filter, Clock Multiplier Factor adjustment module and field coil current regulating module；It is characterized in that GNSS receiver is defeated Go out to hold the input of 1PPS signals in Connection Time blank signal generation module, the output end of time interval signal generation module connects The input of frequency measurement module time blank signal interface is connect, the output end of time-to-digit converter connects time number in frequency measurement module The input of word switching device interface, the output end Connection Time digital quantizer of time-to-digit converter interface in frequency measurement module Input, the input of the output end connection Kalman filter of frequency measurement module, the output end of Kalman filter are divided into two-way, The input of Clock Multiplier Factor adjustment module is connected all the way, and another way connects the input of field coil current regulating module, and CPT is former Crystal oscillator output end is divided into three tunnels in secondary clock, all the way Connection Time blank signal generation module clock signal input terminal, and another way connects Connect frequency measurement module clock signal input, the 3rd tunnel Connection Time digital quantizer clock signal input terminal.Above-mentioned functional module It can be realized in the controller by writing code.
As it will be easily appreciated by one skilled in the art that the foregoing is merely illustrative of the preferred embodiments of the present invention, not to The limitation present invention, all any modification, equivalent and improvement made within the spirit and principles of the invention etc., all should be included Within protection scope of the present invention.

Claims (8)

  1. A kind of 1. method that Atomic Clocks Based on Coherent Population Trapping output frequency is corrected using GNSS, it is characterised in that including following steps Suddenly：
    S1：Using the frequency of 1PPS signal measurement CPT atomic clocks, the difference of frequency measurement and predeterminated frequency is inclined as frequency Difference；
    S2：According to the frequency departure by the frequency correction of CPT atomic clock output signals to predeterminated frequency；
    Step S1 is specially：
    S11：Generate the correcting controlling signal that the cycle is T；
    S12：1PPS signals according to GNSS inputs generate n time interval signal in a cycle T；
    S13：Utilize the frequency of time interval signal measurement CPT atomic clock output signals, a time interval signal measurement record One CPT atomic clock output signal；
    S14：Multiple measured values are obtained in a cycle of the correcting controlling signal, the average value of multiple measured values is carried out Actual output frequency after Kalman filtering processing as CPT atomic clocks within the cycle；And by the actual output frequency with Frequency departure of the difference of default frequency as CPT atomic clocks.
  2. 2. the method as described in claim 1, it is characterised in that step S11 is specially：
    By carrying out cycle count to the frequency of CPT atomic clock output signals, periodic correcting controlling signal is obtained；Wherein, A cycle is that T correcting controlling signal is made up of a high level and a low level, and the duration of high level is T-t0, The low level duration is t0, t0Span be 1us-1ms.
  3. 3. method as claimed in claim 2, it is characterised in that in the high level lasting time of the correcting controlling signal Interior measurement CPT atomic frequency deviations, according to frequency departure by CPT atomic clock output signals in the low duration Frequency correction to default frequency.
  4. 4. the method as described in claim 1, it is characterised in that step S12 is specially：
    By carrying out cycle count to the frequency of CPT atomic clock output signals, periodic multiple-pulse signal strobe is obtained；
    The pulse gate signal of H groups two is obtained according to the multiple-pulse signal strobe；
    Each two pulse gates signal obtains a time interval signal by capturing 1PPS rising edge, and n time is obtained Blank signal；Wherein H value is equal with n values.
  5. 5. method as claimed in claim 4, it is characterised in that obtaining the pulse gate signal of H groups two is specially：
    There are 2n pulse high level, each pulse high level duration in a cycle T of the multiple-pulse signal strobe It is less than 2s more than 1s, the spacing of preceding n rising edge of a pulse is ks, and the spacing of rear n rising edge of a pulse is also ks；1st pulse Spacing between the rising edge of high level and the rising edge of (n+1)th pulse high level is T', the 1st pulse and (n+1)th arteries and veins To rush as first group, n-th of pulse that the 2nd pulse and the n-th+2 pulses are second group ... ... and the 2n pulse are H groups, according to It is secondary to analogize acquisition H group pulses, include high level and low level per group pulse, a two pulse gate signals are formed per group pulse, The rising edge spacing of two pulses of two pulse gate signals is T', obtains the pulse gate signal of H groups two altogether；Two pulse gates are believed Number cycle be T；Wherein, k is the integer more than 1.
  6. 6. method as claimed in claim 4, it is characterised in that obtaining a time interval signal is specially：Corrective control is believed Number a cycle T in, two pulse gate signals have two pulse high levels, first pulse high level duration detection 1PPS rising edge, when 1PPS rising edges arrive, time interval signal puts high level；When second pulse high level continues Between detect GPS 1PPS rising edge, when GPS 1PPS rising edges arrive when, time interval signal sets low level, so as to generate One time interval signal.
  7. 7. the method as described in claim 1, it is characterised in that in step s 13, the frequency of the CPT atomic clocks output signal Rate isWherein, T'=NTc+τ1-τ2, Tc=1/fc, N is when the high level of time interval signal continues The number of the CPT atomic clock output signal rising edges of interior measurement；τ1、τ2The error brought for direct counting method, T' is between the time Every high level lasting time, T in signal a cyclecFor the cycle of CPT atomic clock output signals.
  8. 8. the method as described in claim 1, it is characterised in that in step s 2, when CPT atomic clock output signals frequency with When difference between default frequency is more than the threshold value of setting, using coarse adjustment by the frequency correction of CPT atomic clock output signals extremely Predeterminated frequency；
    When the difference between the frequency and default frequency of CPT atomic clock output signals is less than the threshold value of setting, using fine tuning By the frequency correction of CPT atomic clock output signals to predeterminated frequency.
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CN105717784B (en) * 2016-01-29 2018-10-02 北京市计量检测科学研究院 Electric power time service method
CN105811972B (en) * 2016-03-11 2019-02-22 清华大学 A kind of pulsed coherent layout Trapping of Atoms clock magnetic field servo-system
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CN108199712B (en) * 2017-12-01 2021-07-13 北京无线电计量测试研究所 Frequency taming control circuit of CPT atomic clock
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CN109474276B (en) * 2018-12-24 2022-09-23 北京无线电计量测试研究所 CPT atomic clock frequency synchronization control method and system
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